1. Field of the Invention
The present disclosure relates to synthesis methods of preferentially growing single-walled carbon nanotubes (“SWNT”s) with metallic conductivity. Selective growth of SWNTs, particularly with metallic conductivity, is a most challenging obstacle in the synthesis of nanomaterials, and such growth is crucial for high performance electronics. Although significant efforts have been made to separate semiconducting from metallic nanotubes from a single synthesis, or to enrich nanotube material with one type of nanotube, development of a direct controllable growth method has been evasive. As a result, no method exists to date to selectively grow nanotubes of a particular chirality.
2. Description of the Related Art
Despite their unique electronic properties, carbon nanotubes have yet to see ubiquitous application in electronic devices. The electronic properties of carbon nanotubes are related to their structure, most specifically to the exact bonding configuration (known as its “chirality”). However, no established synthesis method exists to grow a population of nanotubes of a particular chirality and, importantly, it is also unclear as to what factors determine chirality at the instant of nanotube nucleation.
There have been significant achievements in separating SWNTs according to their conductivity and also in enriching the distribution of nanotubes with a specific conductivity. However, there have been a few reports regarding direct control over nanotube structure during growth. The fact that SWNTs with narrow chiral distributions have been successfully grown indicates that there may be a specific mechanism which controls chirality. The concept of amplifying existing SWNT distributions by “seeding” growth from another nanotube with well-defined chirality has also been proposed; however, evidence for the maintenance of chirality has not yet been reported. The preferential growth of nearly 90% to 96% of semiconducting SWNTs by plasma-enhanced CVD has been reported, but the mechanism that leads to this selectivity remains unclear.